The Jeffree cell was an early

acousto-optic modulator An acousto-optic modulator (AOM), also called a Bragg cell or an acousto-optic deflector (AOD), uses the acousto-optic effect to diffract and shift the frequency of light using sound waves (usually at radio-frequency). They are used in lasers ...

, best known for its use in the

Scophony Scophony was a sophisticated mechanical television system developed in Britain by Scophony Limited. A black and white image was produced by an early form of acousto-optic modulation of a bright light using a piezoelectric crystal and water or othe ...

system of

mechanical television Mechanical television or mechanical scan television is a television system that relies on a mechanical scanning device, such as a rotating disk with holes in it or a rotating mirror drum, to scan the scene and generate the video signal, and a si ...

. It was invented by J.H. Jeffree in 1934, and was a major improvement over the

Kerr cell The Kerr effect, also called the quadratic electro-optic (QEO) effect, is a change in the refractive index of a material in response to an applied electric field. The Kerr effect is distinct from the Pockels effect in that the induced index chan ...

modulators used up to that time by allowing more than 200 times the available modulated light. Using ultrasonic sound waves travelling perpendicular to the light, the modulator created areas of varying

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

leading to advancement and retardation of portions of the light wavefront. This led to constructive and destructive interference among the light waves, modulating their intensity.

External links

Scophony system at Early Television website

References

Optical devices {{tech-stub